1. Field of the Invention
The present invention relates to the subject matter of couplings and to a method of coupling shafts without the need to drill or to perform significant machining on the shafts to be connected.
A particular application of the present invention resides in the coupling of composite shafts, i.e., shafts fabricated from continuous filaments in either a roving or tape form within a resin matrix.
The shafts and couplings may be used in a static structural application or in a dynamic environment where they may be required to transmit torque and power.
2. Prior Art
There are many varieties of shaft couplings. For the most part, the shaft to be coupled must be modified in some way to accommodate the coupling. For example, holes may have to be drilled in the shaft to accommodate bolts or other fastening means; the shaft may have to be grooved to accommodate keys or the like; or the shaft may be subjected to excessive compression due to press fitting. All of these methods detract from the advantages of the continuous filament structural design, in that the load transmission capacity of the shaft is substantially reduced through the interruption of the filaments by drilling holes or any machining which will cut the filaments. Further, if the composite shaft is subjected to alternating loads, the stress concentration in the areas of interrupted fibers could result in premature failure. The development of continuous roving or tape wound shafting has introduced a redundant and forgiving structure when compared with the rapid crack propagating and notch sensitive characteristics of metal structures. However, the use of holes or grooves for coupling purposes in composite shafts detracts from the advantages of the composite material, hence it would be desirable to eliminate cutting of fibers in any of the stressed areas.